The Application Values Of T-SPOT.TB In The Diagnosis Of Extra Pulmonary Tuberculosis

Objective:Toevaluate the application values of T-SPOT.TB in the diagnosis of extra pulmonary tuberculosis.Method:We conducted a retrospective study enrolling 280 patients of extra pulmonary tuberculosis who were idendified of mycobacterial species by reverse dot blot hybridization(molecular pathological tests)in the department of pathology in the 309 th hospital of Chinese people’s liberation army from January 2013 to December 2015.We assessed the value of peripheral blood T-SPOT.TB assay for the diagnosis of extra pulmonary tuberculosis through comparing T-SPOT.TB test results and the diagnosis of molecular pathology in routine clinical practice.The index of application values were evaluatdbySensitivity,specificity,positive predictive value,negative predictive value,positive likelihood ratio and negative likelihood ratio.Results:We compared the results of the molecular pathological tests and the T-SPOT.TB.Among the 280 cases,there were 170 cases who got the positive T-SPOT.TB results,and 110 cases who got the negative results.There was 1 case who got the MCH positive molecular pathological results,there were5 cases who got the MGO positive molecular pathological results,146 cases who got the MTC positive molecular results,and 128 cases who got the negative molecular results;There were 148 cases who got the positive T-SPOT.TB results and the positive molecular pathological results,22 cases who got the negative molecular pathological results and the positive T-SPOT.TB results,4 cases who got the positive molecular pathological results and the negative T-SPOT.TB results,and 106 cases who got the negative results of both tests.Sensitivity of T-SPOT.TB for extra pulmonary tuberculosis was 97.4%,and specificity was 82.8%,positive predictive value was 87.0%,negative predictive value was 96.4%,positive likelihood ratio was 5.69,and negative likelihood ratio was 0.0318.Among the 280 cases,Bone,joint and spine specimens accounts for 54.64%(153/280),we list this type separately and give an analysis.Sensitivity of T-SPOT.TB for bone,joint and spine tuberculosis was 80.0%,and specificity was 100.0 %,positive predictive value was 100.0%,negative predictive value was 83.9%,positive likelihood ratio was 5.69,and negative likelihood ratio was 0.0318.We compare the clinical results and the T-SPOT.TB results.There are 170 cases who got the positive T-SPOT.TB results,110 cases who got the negative T-SPOT.TB results,192 cases who got the positive clinical results,and 88 cases who got the negative T-SPOT.TB results.There are 145 cases who got the positive results of both the clinical results and the T-SPOT.TB results,25 cases who got the negative results of clinical results and the positive results of T-SPOT.TB results,47 cases who got the positive clinical results and the negative T-SPOT.TB results,63 cases who got the negative results of both the two tests.Sensitivity of T-SPOT.TB for extra pulmonary tuberculosis was 75.5%(145/192),and specificity was 42.7%(63/88),positive predictive value was 85.3%(145/170),negative predictive value was 57.3%(63/110),positive likelihood ratio was 2.66,and negative likelihood ratio was 0.342.Conclusion:The study suggests that T-SPOT.TB tests has high sensitivity for the diagnosis of extra pulmonary tuberculosis,which can provide strong evidence of clinical diagnosis of extra pulmonary tuberculosis.High NPV of T-SPOT.TB for the diagnosis of extra tuberculosis illustrates that the supplementary role of the test for the diagnositic exclusion of extra pulmonary tuberculosis,although the low PPV limits its usefulness in routine clinical practice in China,where prevalence of latent TB infection is high.